<template>
  <div class="pagination">
    <button :disabled='pageNo==1' @click="handlePageChange(pageNo-1)">上一页</button>
    <button v-show="startNumAndEndNum.start>1" @click="handlePageChange(1)" :class="{'isActive':pageNo==1}">1</button>
    <button v-show="startNumAndEndNum.start>2">···</button>

    <!-- 中间连续页码 -->
    <!-- v-for可以处理的数据类型：Array | Object | number | string | Iterable -->
    <button v-for='(page,index) in startNumAndEndNum.end' :key="index" v-show="page>=startNumAndEndNum.start"
      @click="handlePageChange(page)" :class="{'isActive':pageNo==page}">
      {{page}}
    </button>

    <button v-show="startNumAndEndNum.end<totalPage-1">···</button>
    <button v-show="startNumAndEndNum.end<totalPage" @click="handlePageChange(totalPage)" :class="{'isActive':pageNo==totalPage}">{{totalPage}}</button>
    <button :disabled='pageNo==totalPage' @click="handlePageChange(pageNo+1)">下一页</button>

    <button style="margin-left: 30px">共 {{total}} 条</button>
  </div>
</template>

<script>
export default {
  // 手写分页器
  name: "Pagination",
  props: ["pageNo", "pageSize", "total", "continuous"],
  computed: {
    totalPage() {
      return Math.ceil(this.total / this.pageSize);
    },
    startNumAndEndNum(){
      let start=0
      let end=0
      // 如果显示的连续页码大于总页数
      if(this.continuous>this.totalPage){
        start=1
        end=this.totalPage
      }else{
        start=this.pageNo-Math.floor(this.continuous/2)
        end=this.pageNo+Math.floor(this.continuous/2)
        if(start<1){
          start=1
          end=this.continuous
        }
        if(end>this.totalPage){
          end=this.totalPage
          start=this.totalPage-this.continuous+1
        }
        return {start,end}
      }
    }
  },
  methods: {
    handlePageChange(pageNo){
      this.$emit('changePage',pageNo)
    }
  },
};
</script>

<style lang='less' scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.isActive{
  background: skyblue !important;
}
</style>